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A269823 Number of nX2 0..4 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling four exactly once. 1
5, 216, 3096, 39784, 462680, 5145736, 55265336, 580002280, 5978552216, 60784629832, 611189228792, 6090202880680, 60229576820312, 591855697435912, 5784216137341880, 56261693581866856, 544976552619855128 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 10*a(n-1) + 47*a(n-2) - 336*a(n-3) - 1416*a(n-4) - 864*a(n-5) - 144*a(n-6) for n>7.

Empirical g.f.: x*(5 + 166*x + 701*x^2 + 352*x^3 - 1016*x^4 - 480*x^5 + 720*x^6) / (1 - 5*x - 36*x^2 - 12*x^3)^2. - Colin Barker, Jan 29 2019

EXAMPLE

Some solutions for n=4:

..4..2. .2..0. .1..1. .3..3. .1..4. .4..2. .1..1. .3..3. .2..4. .2..3

..1..4. .0..3. .4..2. .2..2. .2..0. .1..1. .2..0. .4..4. .3..0. .0..4

..1..2. .2..0. .3..0. .4..4. .0..0. .4..2. .1..2. .2..1. .3..3. .1..1

..2..0. .4..3. .3..0. .4..4. .1..2. .3..2. .1..4. .0..2. .2..0. .2..1

CROSSREFS

Column 2 of A269829.

Sequence in context: A048433 A270870 A144796 * A206457 A291806 A119657

Adjacent sequences:  A269820 A269821 A269822 * A269824 A269825 A269826

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 05 2016

STATUS

approved

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Last modified January 26 07:21 EST 2022. Contains 350573 sequences. (Running on oeis4.)